1. Field of the Invention
This invention relates to illuminated alphanumeric displays, and more particularly to a low power, long life illuminated alphanumeric display module which can be easily combined with other display modules.
2. Description of the Prior Art
Combinations of numbers are universally displayed on domestic and commercial buildings to identify the street address of the building. These numbers are usually fabricated of a solid material which contrasts with the color of the building to make the numbers readily visible. However, such numbers are generally not visible at night, thus making nighttime identification of a building having a known address difficult.
Attempts have been made to make building identification numbers as visible at night as they are in the day. These attempts have generally involved mounting an incandescent light behind a light transmissive plate having the identification numerals marked thereon. These incandescent light displays are readily visible at night and thus solve the aforementioned problems associated with conventional non-illuminated numerals. However, they have not met with popular acceptance due, primarily, to their choice of a light source. The incandescent lights which are used require a fairly high power and thus have a significant operating expense. Further, their high power consumption precludes the use of batteries, solar cells or the like to power the bulb. Additionally, incandescent lights must be replaced fairly often.
Recently, sheets of a luminescent material have been used to provide illumination for alphanumeric displays. These electroluminescent sheets are basically a capacitor having two conducting surfaces with a dielectric therebetween. A luminescent pigment is dispersed within the dielectric so that a high frequency, fairly high voltage signal applied between the two conducting surfaces causes current to flow through the dielectric, thereby causing the pigment to glow. The primary advantage of these electroluminescent sheets as a display is their low power consumption and long, useful life. These devices have been used as alphanumeric displays, but always by placing a continuous luminescent sheet behind an opaque mass having transparent alphanumeric characters through which the luminescent sheet is exposed.
Either of the above-described illuminated alphanumeric displays are somewhat inflexible in that the display must be manufactured to display a specific combination of alphanumeric characters. It is relatively difficult to vary the combination of characters, and manufacture of the display is thus a custom project.